All-optical production of 6Li quantum gases

Abstract

We report efficient production of quantum gases of 6Li using a sub-Doppler cooling scheme based on the D1 transition. After loading in a standard magneto-optical trap, an atomic sample of 109 atoms is cooled at a temperature of 40 μK by a bichromatic D1 gray-molasses. More than 2×107 atoms are then transferred into a high-intensity optical dipole trap, where a two-spin state mixture is evaporatively cooled down to quantum degeneracy. We observe that D1 cooling remains effective in the deep trapping potential, allowing an effective increase of the atomic phase-space density before starting the evaporation. In a total experimental cycle of 11 s, we produce weakly-interacting degenerate Fermi gases of 7×105 atoms at T/TF < 0.1 and molecular Bose-Einstein condensates of up 5×105 molecules. We further describe a simple and compact optical system both for high-resolution imaging and for imprinting a thin optical barrier on the atomic cloud; this represents a first step towards the study of quantum tunneling in strongly interacting superfluid Fermi gases.